Modifying keyspace in Cassandra

Cassandra is a distributed NoSQL database that can handle a large amount of data. In Cassandra, data is organized and stored in keyspaces, which are the top-level containers that group tables together. Keyspace modification is a critical task in Cassandra that allows you to create, modify, and drop keyspaces to manage your data more efficiently. In this article, we will discuss the different ways to modify a keyspace in Cassandra with examples.

Introduction

In Cassandra, a keyspace is a namespace that defines the scope of data replication. It contains one or more tables. Each table has its own column family. A keyspace in Cassandra is a data container, such as a database in an RDMBS (Relational Database Management System). It also determines how data replicates across nodes.

Modifying Keyspace in Cassandra

Modifying the keyspace is a critical task in Cassandra. This allows you to create new keyspaces. It also allows modifying existing keyspaces and deleting unnecessary keyspaces. Keyspace modification lets you configure the replication strategy and modify the column families in your keyspace.

Creating a new keyspace

You can use the CREATE KEYSPACE command followed by the keyspace name. Then configuration parameters. For example

CREATE KEYSPACE mykeyspace
WITH replication = {'class':'SimpleStrategy', 'replication_factor':3};

This command creates a new keyspace named "mykeyspace" with the SimpleStrategy replication strategy and replication factor of 3.

Altering an existing keyspace

You can use the ALTER KEYSPACE command followed by the keyspace name. Then configuration parameters that you want to modify. For example:

ALTER KEYSPACE mykeyspace
WITH replication = {'class':'NetworkTopologyStrategy', 'dc1':3, 'dc2':2};

This command alters the keyspace named "mykeyspace" and changes the replication strategy to NetworkTopologyStrategy with 3 replicas in dc1 and 2 replicas in dc2.

Dropping a keyspace

You can use the DROP KEYSPACE command followed by the keyspace name. For example:

DROP KEYSPACE mykeyspace;

This command drops the keyspace named "mykeyspace". Then deletes all the tables and data in the keyspace.

Advanced Keyspace Modification

These are some of the advanced keyspace modifications which are given below.

Modifying replication strategy

The replication strategy in Cassandra determines how data is replicated across nodes in the cluster. You can modify the replication strategy of a keyspace using the ALTER KEYSPACE command with the replication configuration. For example:

ALTER KEYSPACE mykeyspace
WITH replication = {'class':'NetworkTopologyStrategy', 'dc1':3, 'dc2':2};

This command changes the replication strategy of the keyspace "mykeyspace" to NetworkTopologyStrategy with 3 replicas in dc1 and 2 replicas in dc2.

Adding and modifying column families

A column family in Cassandra is a collection of related columns within a table. You can add and modify column families in a keyspace using the ALTER TABLE command. For example

ALTER TABLE mytable
ADD mynewcolumn text;

You can add new column "mynewcolumn" to the "mytable" using given command. You can also modify the properties of a column family using the ALTER TABLE command. For example:

ALTER TABLE mytable
ALTER mycolumn TYPE text;

This modifies the data type of the "mycolumn" column in the "mytable" table.

Various Components of Cassandra Keyspace

These are the different components of Cassandra keyspace as given below.

Strategy:

This is the method used to declare the strategy name in Cassandra. There are two types of Strategy as given below.

• (a). Simple Strategy This strategy is used when you have just one data center. The first replica is placed on the node selected by the partitioner, and the remaining nodes are placed in the clockwise direction in the ring without considering rack or node location.

• (b). Network Topology Strategy This strategy is used when you have more than one data center. In this strategy, you have to provide replication factor for each data center separately. Network topology strategy places replicas in nodes in the clockwise direction in the same data center. This strategy attempts to place replicas in different racks.

Replication Factor

Replication factor is the number of replicas of data placed on different nodes. A good replication factor for no failure is 3. More than two replication factors ensures no single point of failure. This means that even if a server goes down or there is a network problem, other replicas provide service with no failure.

Example

To create a keyspace in Cassandra, the following command can be used:

Create keyspace University with replication =

{'class':SimpleStrategy,'replication_factor': 3};

This command will create the keyspace "University" in Cassandra with a "SimpleStrategy" and replication factor of 3.

Conclusion

In Cassandra, data is organized and stored in keyspaces, which are the top-level containers that group tables together. You can manage data easily and efficiently. It allows you to create, modify and drop keyspaces, configure replication strategies, and modify column families. In this article, we have discussed the various modified keyspaces in Cassandra.